1. Field of the Invention
The present invention relates generally to electric motors, which are particularly suitable for use as part of a large fan. More particularly, the present invention concerns the rotor of the electric motor, wherein the rotor includes a diecast rotor can and a magnetic backing ring cast into place during formation of the can.
2. Discussion of the Prior Art
In many motor applications, the rotor carries significant loads and must consequently have the structural integrity to operate in these conditions. For example, some motor-driven fans (particularly fans having a diameter greater than one (1) meter) have fan blades supported on the rotor. Such motors often have an outer rotor construction, with the rotor can generally circumscribing the stator and supporting the blades.
The fabrication of a motor with a heavily loaded rotor is often time consuming and costly. More specifically, the rotor can is typically formed of metal and must be machined to facilitate precise mounting and support of the magnets and backing ring. The backing ring is also often machined. In such conventional motor designs, the magnets and backing ring must be appropriately secured to the can, typically with a precise press-fit connection, fasteners, and/or adhesive.
Yet further, the foregoing prior art motor designs often require balancing of the rotor assembly (including any components, such as fan blades, carried by the rotor). For example, in large fans, dynamic balancing of the rotor and blades can often be extremely time consuming (e.g., balancing operations can often exceed fifteen (15) minutes).